Bonus data from old plans ... does it expire?

I noticed that the "bonus data" offered on new plans have a 24 month expiry date. I have an older plan with "bonus data" and I'm worried that it may also expire at some point, given that Koodo is moving in that direction. Should I be concerned? Is there a way to tell if your "bonus data" is permanent or will expire?

For clarity, I have a 2GB +2GB plan for $65 and I noticed that Koodo now has a 4GB plan for $65. However, the price for overages goes from $5 to $7 per mb. I rarely go over, but if my bonus data is permanent, there's no sense in switching to the plan with the higher overage rate ... just in case.